Various types of coil planet centrifuges have been developed for separating solutes and/or particles on the basis of partition coefficients and/or elutriation. Among the various schemes, the most efficient separations have been achieved from those utilizing coiled tubes rotating in an acceleration field of either gravitational or centrifugal origin. Several schemes to perform continuous countercurrent extraction have been described, such as employing a flow-through coil planet centrifuge (see U.S. Pat. No. 4,151,089 to Y. Ito) and inducing a homogeneously circulating force field around the coiled tube (see U.S. Pat. No. 3,775,309 to Y. Ito et al). A prior art arrangement providing heterogeneously circulating centrifugal force fields around the coiled tube, as utilized in the present invention, is exemplified in connection with the horizontal flow-through coil planet centrifuge disclosed in U.S. Pat. No. 4,058,460 to Y. Ito, and also in a toroidal coil planet centrifuge apparatus disclosed in U.S. patent application Ser. No. 45,052, of Y. Ito. Another system of cell separation and plasmapheresis, relative to which the present invention is an improvement and simplification, is disclosed in U.S. patent application Ser. No. 661,114, of Y. Ito, employing no rotating seals. In this system, however, a large portion of the flow tubes is subjected to revolution around the central axis of the apparatus, which limits the applicable centrifugal force field to the column.